A somewhat tricky way - a text link with only one space as text:

…alternatives Format:   

The wiki code:

...alternatives Format: \_\_ {{sensitivity.pdf| }}

(The two \_ are &nbsp-entities, just for the gap. Defined in the file:  entities.local.conf .)

The PDF icon is not shown in my old inbuilt browser on my old smartphone (first released 2011). Not explored yet. Current browsers are not affected – status october 2018.

https://forum.dokuwiki.org/post/63013